In the field of aerospace propulsion, the widespread use of traditional hypergolic rocket engine propellants, such as hydrazine and nitrogen tetroxide, are being eliminated. Presently, there is a movement toward the development of inexpensive rocket engine fuel systems that use non-toxic propellants. High test hydrogen peroxide/kerosene offers similar performance per unit volume as Liquid Oxygen (LOX) and kerosene for Single Stage To Orbit (SSTO) vehicles. High test hydrogen peroxide has been employed as a rocket engine oxidizer for over half a century, and has been used in military rocket-assisted aircraft systems, due to the ease of handling and storing.
Rocket engines traditionally employ a chemical redox process requiring both an oxidizer and a fuel source to generate energy and hot gasses for propulsion. It is known that some oxidizers generate toxic gasses during the redox process. Therefore, an interest in alternative oxidizers that do not generate toxic gasses is of growing importance. Hydrogen peroxide is a leading candidate for use as an environmentally friendly oxidizer source.
Rocket engines are capable of consuming vast amounts of hydrogen peroxide. For example, it is predicted that some rocket engines may require over 1 million pounds of hydrogen peroxide per rocket launch. Thus, the market for highly concentrated hydrogen peroxide within the next 5-10 years could reach over 26 million pounds per year for the U.S. military market alone. These estimates are based upon current use by the Air Force and Navy in rocket propulsion and airborne laser applications. To date, there is a limited supply of hydrogen peroxide in necessary concentrations for rocket propulsion, and current engine developments are hindered by the high cost of obtaining sufficiently concentrated hydrogen peroxide, which at this time, is predominantly satisfied by importation.
Liquid oxygen, a cryogenic liquid has frequently been utilized, but presents many problems. For example, a common problem with liquid oxygen in rocket engines is that of "hard-start," wherein inadequate ignition is provided to the fuel stream. Thus, a mixture of liquid oxygen and fuel can collect and ignite inside the rocket engine thereby causing the disintegration of the engine and launch vehicle. Rocket engines employing highly concentrated hydrogen peroxide can avoid this hazard entirely as hydrogen peroxide engines typically decompose the hydrogen peroxide into hot steam and oxygen gas, which is then mixed with the fuel. Propellants cannot accumulate in the engine due to the onrush of decomposed hydrogen peroxide gas. Previous methods of concentrating hydrogen peroxide have been accomplished by using an inert working gas and vacuum system within a fluorinated reaction vessel, see for example, Tillotson et al., U.S. Pat. No. 5,621,847. However, systems such as the one described in Tillotson et al., are not very economical as the design requires use of a vacuum. Also, such systems do not have the capability of using air to evaporate water from a dilute solution.